Our research aims to utilize non-innocent or redox-active ligand platforms in stoichiometric and catalytic chemical reactions. Currently, we are using this ligand design strategy to favor the multi-electron transformations necessary to address chemical problems such as small molecule activation (O2, N2, CO and CO2 substrates), atom- and group-transfer catalysis (carbonylation, aziridination, epoxidation) and energy conversion (photochemical water splitting).

New Fundamental ReactivityEarly transition metal ions are often strong electrophiles thanks to formal d0 valence electron counts, and as such, they often promote non-redox bond activation reactions. We are utilizing redox-active ligands to bring late-transition-metal reactivity to these early, electrophilic metals. Recently we have reported the first examples of ligand-enabled, oxidative-addition and reductive-elimination reactivity at a d0 zirconium(IV) center.

Atom- and Group-Transfer ReactionsTransition-metal oxo and imido complexes display diverse reactivity patterns. For example, some imido ligands are so stable they act as spectator ligands in polymerization catalysts. At the other extreme, nitrene transfer to unsaturated substrates or nitrene insertion into C–H bonds could provide the basis for attractive catalytic reactions. While late-transition-metal oxo and imido complexes often display reactivity consistent with one-electron (radical) pathways, the strong polarization of early-transition-metal oxo and imido bonds often leads to two-electron (electrophile-nucleophile) reactivity. Unfortunately, the lack of accessible two-electron redox cycles has inhibited the development of catalysts built upon these electrophilic complexes. Our research group is utilizing redox-active ligands in concert with atom- and group-transfer reactions to develop new strategies for hydrocarbon amination and oxidation.

Photochemical Water SplittingThe development of alternatives to fossil fuel energy resources must become the dominant pursuit of the scientific community in the 21st century. One major role for chemists to play is in the development of catalysts that harness abundant solar energy and use it to drive fuel-forming reactions. The ultimate 'green' fuel-forming reaction is the splitting of water into hydrogen and oxygen:

2 H2O + hv ---> 2 H2 + O2

By photochemically splitting water into hydrogen (the fuel) and oxygen (the oxidant), the sun's energy can be stored indefinitely in chemical bonds and released during combustion.

Unfortunately, there is no known catalyst to photochemically split water that is both efficient enough and cheap enough for wide-spread use. Our lab is developing new multimetallic systems with redox-active ligand cofactors for use as catalysts to photochemically split water into hydrogen and oxygen.